1. Field of the Invention
The present invention relates to a fuel injection control device applied to a fuel supply system that supplies fuel to an internal combustion engine.
2. Description of Related Art
Conventionally, as a fuel supply system of a direct-injection gasoline engine, there has been practically used a fuel supply system that has a low-pressure pump for drawing fuel from a fuel tank and for pressurizing the fuel, a high-pressure pump driven by an engine for further pressurizing the fuel discharged by the low-pressure pump and a delivery pipe for storing the fuel pumped from the high-pressure pump and that injects the high-pressure fuel in the delivery pipe from the injector directly into a cylinder of the internal combustion engine (for example, as described in Patent document 1: JP-A-H9-209804). Generally, in such the system, pressure of the fuel in the delivery pipe is regulated to target pressure by controlling fuel pumping quantity of the high-pressure pump. Fuel injection quantity of the injector changes with injection pressure during the fuel injection, i.e., the pressure of the fuel in the delivery pipe. Therefore, the fuel injection quantity is set based on an operation state of the engine and a fuel injection period is set based on the fuel injection quantity and the pressure of the fuel in the delivery pipe (for example, as described in Patent document 2: JP-A-H9-195819).
The high-pressure pump repeats suction and discharge of the fuel in synchronization with a crank angle of the engine, and the pressure of the fuel in the delivery pipe rises at every discharge of the high-pressure pump. Therefore, if the fuel injection is performed such that the fuel injection overlaps with the pressure increase, an error arises in the fuel injection quantity.